1. Field of the Invention
The application relates to a method and a device for controlling the transmission power in transmission systems, in particular in mobile radio systems, and a transceiver device adapted thereto.
2. Description of Related Art
In mobile radio systems, transceiver devices are housed in “cabinets” of base stations (BTS). The base stations are in turn conventionally divided up into a plurality of radio cells, referred to as sectors, one base station normally covering three sectors. A plurality of carriers are available for information transmission for each cell or sector, depending on the communication network which is used. In a UMTS-based network (Universal Mobile Communication System), i.e. a third-generation mobile radio network, there are, for example, a maximum of three carriers available per cell.
If a plurality of carrier frequencies are available per cell, the transmission signals of the various transmission devices are initially combined in a conventional manner via “hybrid combiners” to form one output signal, and are then fed to a common antenna. In order to operate in diversity mode within one cell, two antennas are essentially required per carrier, the antennas normally being designed for transmission and reception. However, in order to ensure transmission and reception via one antenna, “duplexers” are furthermore required in order to separate the transmission and reception frequency bands. One hybrid combiner and in particular one duplexer of one base station therefore conventionally cover the entire available frequency range, i.e. in a UMTS system, this means one frequency range of around 60 MHz for Europe.
However, limits are specified by international standards in respect of stop-band attenuation inside (inband) and outside (out-of-band) the frequency band. Particularly the inband limits in UMTS frequency bands impose demanding requirements in terms of emitted interference. These international standards, such as, in particular, the 3GPP standard for UMTS systems, do not provide for internal frequency subdivision between different network operators. The transmission amplifiers and filters used in current base stations are therefore correspondingly designed in such a way that they cover the entire available frequency band. In a current broadband implementation, the corresponding system parameters must therefore satisfy the critical requirements in both the transmission amplifier and the filter in order to be able to adhere to the prescribed limits, which results in increased production and operating costs.
The associated industrial and ecological disadvantages are all the more significant because network operators operate networks within specific frequency bands ranging over a plurality of mobile radio standards, such as GSM, (Global System for Mobile Communication), UMTS, TDMA (Time Division Multiple Access). Not only transmission devices for broadband UMTS transmission signals, but also transmission devices for narrower-band GSM transmission signals must be provided. In the GSM-based networks too, duplexers are used for this purpose in a manner known per se to separate the transmission and reception bands, along with “filter combiners” with filters which can be tuned over the entire frequency range to combine a plurality of transmission signals.